This invention relates to movable shaft assemblies for movement of an array of adjustable members. More particularly. it relates to torque shaft assemblies in power generating apparatus such as gas turbine engines.
Turbine engines with variable airfoil capability, for example variable compressor stator vanes, frequently include a torque shaft assembly associated with an actuator. Such an assembly enables and coordinates movement of a plurality of stages of stator vanes responsive to controlled, changing engine conditions. Examples of gas turbine engines including axial flow compressors having variable stator mechanisms is shown in U.S. Pat. Nos. 2,858,062--Allen (patented Oct. 28, 1958) and 2,933,235--Neumann (patented Apr. 19, 1960).
Currently used torque shaft assemblies, as well as those shown in the above identified patents, include solid metal shafts into which generally are provided recesses, slots, indentations, etc., within the outer surface of the shaft to receive or provide connection with other assembly parts, for example turnbuckles. Because torque shafts can be subject to undesirable flexural (flex) action resulting from engine vibration, some gas turbine engine solid shafts have been provided with a generally central mount, in addition to end mounts, to restrict such undesirable motion of the shaft. However, in the design of some turbine engines, it has not been practical to provide such a central mount, and solid torque shafts with only end mounts have been used. It has been found that premature wear has been observed with such end-mounted torque shafts, sometimes in a very short period of time. For example, such wear has occurred on forward shaft journals and on aft spherical bearings. Means to restrict or change the occurrence of undesirable motion of such end-mounted shafts to avoid premature wear would reduce the need for early repair or replacement of torque shafts.